1. Technical Field
The present invention relates to a Ca—Na—SiO2—Al2O3/Sodium-Calcium-Aluminosilicate composition, a method of making Ca—Na—SiO2—Al2O3/Sodium-Calcium-Aluminosilicate composition, and a method for using the Ca—Na—SiO2—Al2O3/Sodium-Calcium-Aluminosilicate as an adsorbent for the removal of CO2 from a gaseous composition.
2. Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Environmental pollution is one of the major problems facing humanity this century. Emission of toxic gases into the atmosphere is a primary source of air pollution. Combustion of heavy oil, coal and oil shale, exhausts from automobiles, as well as smelting operation, sulfuric acid manufacturing and metallurgical processes are the main sources for discharging of these toxicants into the atmosphere. These gases include: sulfur oxides (SOx), nitrogen oxides (NOx), carbon oxides (COx) and hydrogen sulfide (H2S). Once these gases enter the troposphere, some of them react with water and oxygen molecules to form acid rain and return back to the ground. Other gases such as carbon dioxide and fluorinated hydrocarbons can escape to the outer layer of the atmosphere leading to depletion of the ozone layer and affect global warming.
Carbon dioxide specifically reached an alarming level in the atmosphere where a major change in global climate was noticed since the beginning of the 21st century. It is estimated that the net increase of 13,000 million tons of CO2 is added to the atmosphere annually1. The rising level of CO2 is already affecting the atmosphere, sea level and ecological systems. The global sea level has raised 10 to 20 cm over the past century. In this current century this level is expected to rise by 88 cm. The current atmospheric concentration of carbon dioxide is 391.8 ppm, which is 30% greater than that of the pre-industrial level.
Natural gas accounts for emission of large quantity of CO2. In 2004 the global emission of CO2 from natural gas was 5.3 billion tons, while coal and oil produced 10.6 and 10.2 billion, respectively. This value is expected to increase to 11 billion tons which exceeds the one from combustion of coal and oil2.
Adsorption is a promising technology for capturing of CO2 from exhaust gas downstream. The advantage of this process is to utilize low cost adsorbents, naturally occurring materials or by-products of chemical industries that have high removal capacity. Among these materials are activated carbons, zeolites, fly ash, limestone and different metal oxides6-12.
Limestone and kaolin are natural abundant materials which have large reserves worldwide. The main uses of these materials are in the cement industry and in the architectural industry.
Adsorption of carbon dioxide can be attained by different types of adsorbents. Generally those adsorbents can be classified into three different groups; organic-based materials, inorganic solids containing some transition metals, or activated carbonaceous materials. Several research articles were published in this regard. A summary of the most recent and promising results is provided below:
Sevilla and Fuertes14 utilized activated carbon material prepared for adsorption of CO2 from a CO2—N2 gas mixture. The adsorbent showed a surface area of 1020 m2/g and a pore volume of 0.91 cm3/g which can be enhanced to 2660 m2/g and 1.38 cm3/g, respectively, by treatment with potassium hydroxide at 600-800° C. The sorption capacity was 3.2 mmol CO2/g at 25° C.
Cen et al.15 used commercial activated carbon adsorption of CO2 from effluent of combustion process. A breakthrough adsorption experiment was performed with simulated flue gas of 12 vol. % CO2. The kinetic parameters that affect the rate of adsorption of CO2 in a fixed bed column was evaluated.
Schell et al.16 studied adsorption equilibrium of CO2, H2 and N2 on AP3-60 commercial activated carbon using a Rubotherm Magnetic Suspension Balance and gravimetric-chromatographic method. The results were fitted to Langmuir and Sips isotherms and compared to binary measurements.
Shao et al.17 tested several carbonaceous mesoporous materials for adsorption of CO2 by gravimetric analyzer (IGA-003, Hiden). It was found that CO2 adsorption capacity of 909 mg/g has been achieved by the type ACB-5 at 298 K and 18 bar.
Karadas et at.18 prepared metal carbonates consisting of Zn2+, Mg2+, and Cu2+ and measured the adsorption of CO2 by this material using thermogravimetric analysis (TGA).
Abid et al.19 prepared zirconium-metal organic frameworks (Zr-MOFs) for adsorption of CO2 and CH4. The removal capacities for both gases were 8.1 and 3.6 mmol/g, respectively, obtained at 273K, 988 kPa. Addition of ammonium hydroxide during the synthesis of MOF lowered the sorption capacities but enhanced the selectivity of CO2 over CH4.
Wang et al.20 investigated the ability of Si-doped lithium zirconate sorbents for adsorption of CO2. Doping silicon in the adsorbent matrix could improve the sorption capacity.
Modak et al.21 synthesized iron containing porous organic polymers (Fe-POPs). The adsorbent possessed a high BET surface area and appreciable CO2 capture of 19 wt % at 273 K and 1 bar.
Kauffman et al.22 evaluated the selectivity of adsorption of CO2 from N2, CH4, and N2O gas mixture by dynamic porous coordination polymer using ATR-FTIR spectroscopy, GC, etc. They proved that all the selected techniques indicate high selective adsorption of CO2 from CO2/CH4 and CO2/N2 mixtures at 30° C., while the system CO2/N2O is not selective.
Wang and Yang23 enhanced the porosity of silica SBA-15 by two template removal methods followed by amine grafting and used for removal of CO2 from CO2/N2 gas mixture. The CO2 sorption capacity was increased from 1.05 to 1.6 mmol/g when the silanol density was increased from 3.4 to 8.5 OH/nm2 and the grafted amine loading was increased from 2.2 to 3.2 mmol/g.
Zhao24 investigated the adsorption of CO2 by Mg-modified silica. They developed the Mg-zeolite by methods of co-condensation, dispersion and ion-exchange where Mg2+ ions were introduced into SBA-15 and MCM-41, and transformed into MgO in the calcination process. The adsorption capacity increased from 0.42 mmol/g of pure silica SBA-15 to 1.35 mmol/g of Mg—Al-SBA-15-I1 and increased from 0.67 mmol/g of pure silica MCM-41 to 1.32 mmol/g of Mg-EDA-MCM-41-D10 by ion exchange and dispersion methods, respectively.
Sonawane and Nagare25 investigated theoretically the reactivity of Si-doped single walled carbon nanotubes for O2, CO2, SO2 and NO2 using density functional theory. They showed that the charge density, binding energy and density and charge transfer of state are the main factors for chemical adsorption of these gases by Si-CNT.
Xue et al.26 showed that the selectivity and adsorption capacity of CO2 were increased by addition of piperazine to methyldiethylamine during the modification of the surface of silica gels. The exit concentration from a column packed with this adsorbent has decreased from 13 wt. % to less than 0.05 wt. %.
Li27 investigated the adsorption dynamics of CO2 by a bed of sodium oxide promoted alumina. The breakthrough curve model was developed based on the experimental data.
Zukal et al.28 measured the adsorption isotherm of CO2 on the Na-A zeolite in the temperature range from 273 to 333 K. The data were fitted to a periodic density functional model improved for the proper description of dispersion interactions.
Reinik et al.29 synthesized calcium-silica-aluminum hydrate from oil shale fly ash by reaction with 5M sodium hydroxide at 130° C. The material was tested for its adsorption capacity of CO2 using thermo-gravimetric analysis. The results showed an increase in capacity from 0.06 mass % when using untreated ash to 3-4 mass % after alkaline hydrothermal activation with NaOH.
The present disclosure describes mixtures of aluminosilicates linked with calcium and sodium oxides in a crystalline structure. The materials were used for adsorption of acidic gases such as CO2 from a gas stream.